Yamaha Impeller Housing YJA-01209-33-02. Overview. The Yamaha YJA-01209-33-02 Impeller Housing is a genuine original equipment manufacturer component designed to support the water pump system and maintain efficient engine cooling. The impeller housing forms the chamber where the water pump impeller rotates, allowing cooling water to be drawn in and circulated through the engine's internal cooling passages.. A properly functioning impeller housing ensures the impeller operates smoothly and mainta